1. Field of the Invention
The present invention relates to a polyphenylene sulfide resin composition and a molded component made from such a resin composition, and in particular, to an electrophotographic transfer belt. More specifically, the present invention relates to a polyphenylene sulfide resin composition that is superior in toughness typically represented by impact strength, tensile extension, or the like and exerts a good uniform dispersibility when carbon is dispersed therein, and a molded component made from the resin composition, in particular, an electrophotographic transfer belt.
2. Description of the Related Art
The polyphenylene sulfide resin (hereinafter, referred to as “PPS resin”) has suitable properties as an engineering plastic material, such as excellent heat resistance, flame resistance, rigidity, chemical resistance and electrical insulating property, and is used for various electric and electronic parts, mechanical parts and automobile parts, mainly as injection molding products. However, the PPS resin is not sufficiently superior in toughness in comparison with other engineering plastic materials such as polyamide resin. For this reason, in most cases, the PPS resin is conventionally used in combination with a reinforcing agent such as glass fibers so as to improve the strength thereof.
In recent years, however, in order to meet demands for light weight, surface smoothness, and the like, there have been strong demands for the PPS resin as a non-reinforced material without using glass fibers or the like, and a non-reinforced PPS material having superior toughness has been requested.
As a method for improving the toughness of the non-reinforced PPS material, a PPS resin composition containing a polyamide resin has been known. For example, as described in JP-B No. 59-1422, JP-A No. 53-69255 and JP-A No. 6-49356, various attempts have been made so as to improve the toughness of PPS by blending a material that is superior in toughness therein. If the PPS and polyamide were dissolved uniformly like sugar dissolved in water, the problem would be solved by using the techniques as described therein. However, as described in J. MACROMOL. SCI. PHYS., B41(3), 407-418(2002), Jung-Bum An, Takeshi Suzuki, Toshiaki Ougizawa, Takashi Inoue, Kenji Mitamura and Kazuo Kawanishi, upon blending the PPS in polyamide, the two components are hardly compatible with each other, and it has been confirmed that although only 4,6-nylon is compatible therewith at a high temperature of 300° C. or more, a phase separation occurs when cooled off. As has been well-known, remarkable improvements in physical properties are achieved when upon blending a polymer and an elastomer, the two components are made compatible with each other; however, as described in the above J. MACROMOL. SCI. PHYS., B41(3), 407-418(2002), no such combination has been found in the PPS. Consequently, the blending with another elastomer fails to provide an effective method for improving a strength property, and tends to impair not only a high modulus of elasticity, but also other superior characteristics, such as a burning property, in which the PPS possesses.
On the other hand, JP-A No. 9-291213 and JP-A No. 62-197422 have disclosed an oxidized crosslinking PPS resin having superior mechanical strength, which restrains the occurrence of weld cracks; however, this resin is not necessarily superior in toughness properties such as tensile extension and impact strength. Another problem is that oxidation crosslinking treatment is not effectively used for applications in which a molded component is obtained in a continuous producing process, such as an extrusion-molding process.
Upon application of the PPS resin composition to a transfer belt for use in electrophotography, it is necessary to add a conductive agent such as carbon thereto so as to set a conductivity of the resin within a uniform semiconductor area; however, the PPS resin is not necessarily superior in the dispersibility of carbon, and has a disadvantage in that upon extrusion-molding, the dispersion state of carbon changes to cause the nonuniformity of conductivity. The nonuniformity of the conductivity in the transfer belt causes an image loss in characters and toner scattering during durability printing.